The reason I mentioned this is because if the algebraic result,
according to the equations I gave, is

J:
a b
1 3
1 4
2 3
2 4

then J MINUS D = J' MINUS D becomes a contradiction. There might be
other ways for a language to treat that assertion, but I would say the
more clear-cut one is to treat it as what it is, a constraint. Since
the algebraic result breaks the constraint, the result is more likely an
empty J value.
Received on Sun Aug 23 2009 - 23:35:43 CEST